Genetics of Natural Competence in Vibrio cholerae and other Vibrios

Abstract

Many Gram-positive and Gram-negative bacteria can become naturally competent to take up extracellular DNA from the environment via a dedicated uptake apparatus. The genetic material that is acquired can (i) be used for nutrients, (ii) aid in genome repair, and (iii) promote horizontal gene transfer when incorporated onto the genome by homologous recombination, the process of “transformation.” Recent studies have identified multiple environmental cues sufficient to induce natural transformation in Vibrio cholerae and several other Vibrio species. In V. cholerae , nutrient limitation activates the cAMP receptor protein regulator, quorum-sensing signals promote synthesis of HapR-controlled QstR, chitin stimulates production of TfoX, and low extracellular nucleosides allow CytR to serve as an additional positive regulator. The network of signaling systems that trigger expression of each of these required regulators is well described, but the mechanisms by which each in turn controls competence apparatus genes is poorly understood. Recent work has defined a minimal set of genes that encode apparatus components and begun to characterize the architecture of the machinery by fluorescence microscopy. While studies with a small set of V. cholerae reference isolates have identified regulatory and competence genes required for DNA uptake, future studies may identify additional genes and regulatory connections, as well as revealing how common natural competence is among diverse V. cholerae isolates and other Vibrio species.

Natural Competence Rates Are Variable Among Xylella fastidiosa Strains and Homologous Recombination Occurs In Vitro Between Subspecies fastidiosa and multiplex

“…One key knowledge gap is related to the variability of natural competence among strains, as previous studies were based on a few closely related strains belonging to the same subsp., namely, fastidiosa (Kandel et al 2016;Almeida 2011, 2014;Kung et al 2013). Since both genotypic and phenotypic differences have been described in X. fastidiosa strains (Antonova and Hammer 2015;Coletta-Filho et al 2017;Oliver et al 2014Oliver et al , 2015Parker et al 2012;Scally et al 2005), their natural competence abilities could differ, as is the case reported in other naturally competent bacteria (Bossé et al 2009;Coupat et al 2008;Evans and Rozen 2013;Fujise et al 2004;Gromkova et al 1998;Maughan and Redfield 2009;Sikorski et al 2002). Moreover, although IHR has been detected by MLST studies and was hypothesized to lead to plant host shift (Nunney et al 2012;2014a and2014c), there is still no experimental evidence demonstrating the generation of recombinants by mixing two different subspecies.…”

“…In the majority of naturally competent bacteria, competence development is regulated and induced by external environmental cues (Seitz and Blokesch 2013a). Regulatory mechanisms involved in the induction of natural competence have been described in well-studied bacterial systems such as Vibrio cholerae (Antonova and Hammer 2015) and Haemophilus influenzae (Cameron et al 2008).…”

Parallel quorum sensing signaling pathways in Vibrio cholerae

“…Similar to many bacterial pathogens, Vibrio cholerae, the causative agent of cholera, depends on QS to regulate essential cellular processes for survival and adaptation inside and outside of its hosts (Antonova and Hammer 2015, Beyhan, et al 2007, Blokesch 2012, Hammer and Bassler 2003, Shao and Bassler 2014, Shikuma, et al 2009, Suckow, et al 2011, Yildiz, et al 2004, Zheng, et al 2010, Zhu and Mekalanos 2003, Zhu, et al 2002). Since its discovery, the V. cholerae QS system has served as a model to understand how pathogens employ QS for precise temporal control of virulence factor production (Jung, et al 2015, Liu, et al 2006, Liu, et al 2008, Miller, et al 2002, Tsou and Zhu 2010, Zhu and Mekalanos 2003, Zhu, et al 2002).…”

Role of Non-coding Regulatory RNA in the Virulence of Human Pathogenic Vibrios

“…Most studies concerning the family Vibrionaceae have focused on V. cholerae , the species responsible for several outbreaks of cholera in places such as Bangladesh, Kolkata, and more recently Haiti (Antonova and Hammer, 2015). Today it is known that this microorganism produces a series of virulence factors that facilitate its colonization in the intestine, allowing a subsequent illness characterized by watery diarrhea, often fatal if untreated (Bradley et al, 2011; Cheng et al, 2015).…”